Teletypewriter signal enciphering system



Aug. 2a, 1946. G. A. LOCKE TELETYPEWRITER SIGNAL ENCIPHERINGv SYSTEMFiled March 25, 1944 15 Sheets-Sheet l IIIHI' INVENTOR ATTORNEY G. A.LOCKE TELEIYPEWRITER SIGNAL ENCIPHERING SYSTEM Filed March 25, 1944 15Sheets-Sheet 2 A 7' TORNEY Aug. 20, 1946.

G. A. LOCKE 2,406,23

TELETYPEWRITER SIGNAL ENGIPHERING SYSTEM Filed March 25, 1944 15Sheets-Sheet 5 H m8 b2 ATTbRA/EY It INVENTOR a A. Lac/(E Mbb G. A. LOCKETELETYPEWRITER SIGNAL E'NCIPHERING SYSTEM Aug. 20, E946 l5 Sheets-Sheet4 Filed March 25, 1944 xii INVENTOR G. A. LOCKE BY ohan" Arron/yakAugQZG, 1946'.

a. A. LOCKE TELETYPEWRITER SIGNAL ENCIPHERING SYSTEM Filed March 25,1944 15 Sheets-Sheet 5 Q l 5 lNl ENTOR By G. A. LOC/(E ATTOR/Vy WNNiAug. 20, 1946. OC 2,406,023

TELETYPEWRITER S I GNAL ENC IPHERI N G SYSTEM Filed March 25', 1944 .15Sheets-Sheet 6 ATTORNEY Aug. 20, 1946. e. A. LOCKE TELETYPEWRI'IERSIGNAL ENCIPHERING SYSTEM Filed March 25, 1944 15 Sh eets-Sheet 7 'IIIHINVENTOR 6. A. LOG/(E 7 4... ac

ATTORNEY Au 20, 1946. G, A, L CKE 2,406,023

TELETYPEWRITER SIGNAL ENCIPHERING SYSTEM Filed March 25, 1944 15Sheets-Sheet 8 FOLARIZED VENTOR 0. 2. LOG/(E BY d. a c-wz ATTORNEY Au.20, 1946. 5. A. LocKE TELETYPEWRITER SIGNAL ENCIPHERING SYSTEM 15Sheets-sheet 9 Filed March 25, 1944 lNl ENTOR 6. A. LOCKE BY 1.4.. E.

ATTORNEY Aug. 20, 1946. LOCKE TELETYPEWRITER SIGNAL ENGIPHERING SYSTEMFild March 25, 1944 Q at INVENTOR G A. LDC/(E a... e. cwid ATTORNEY Aug.20, 194. s. A. LOCKE V TELETYP EWRITER SIGNAL ENCIPHERING SYSTEM 15Sheets-Sheet 12 m u 0 E s R F r E 0 0 N m m w.

n Mm A 4 F n own A E E a u m Fmw mmw E:

Filed March 25, 1944 PROFILE OF ENCIPI'IERING AUXILIARY CAM CAM FLAN ERK M m NL c w NA by Wk ATTORNE Y Aug. 20, 1946. e. A. LOCKETELETYPEWRITER SIGNAL ENCIPHERING SYSTEM 15 Sheets-Sheet 15 Filed March25, 1944 ddQlS )NVENTOR G. A. LOCKE BY 3n... ea -4 ATTORNEY PatentedAug. 20, 1946 TELETYPEWRITER SIGNAL EN CIPHERING SYSTEM George A. Locke,Glenwood Landing, N. Y., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationMarch 25, 1944, Serial No. 528,024

23 Claims.

This invention relates to the enciphering of telegraph signals andparticularly to the enciphering of teletypewriter signals.

More particularly this invention is an improved enciphering system forenciphering signals transmitted by a modern teletypewriter in a mannerto provide a neat printed record of an enciphered message by a mechanismwhich dispense-s with the combinations for teletypewriter signalingwhich latter combinations include functional code combinations such asline feed, carriage return, figures, etc., so that such functional codecombinations do not appear in their regular form at ran-- dom in theenciphered message.

Another object of this invention i to devise an improved system toproducea neat, compact typed record of randomly encipheredteletypewriter permutation code combinations which include functionalcode combinations.

Another object of this invention is .the enciphering of permutation codetelegraph signals by means of a system of cams which produce theenciphering permutation code combinations.

A method of enciphering teletypewriter signals which is well known inthe art i the key tape method. In this method permutation codecombination such as Baudot code combinations are punched in a tape inrandom sequence. Each of the permutation code combinations, representingfor instance a letter in a word in a message which is to be enciphered,is modified by one of the code combinations in the key tape. Forinstance, if the first of the five code elements corresponding to theletter is a marking element and the first of the five code elements ofthe enciphering symbol in the key tape is also a marking element, theenciphering mechanism may be arranged so that a marking element will beproduced as the corresponding first element in the resultant encipheredsymbol. If the second of the five code elements corresponding to theletter is a spacing element and the second of the five code elements ofthe enciphering symbol is a marking element a spacing element will beproduced in the enciphered symbol. And, in general, where correspondingelements in the permutation code combination for the text letter and inthe permutation code combination for the enciphering symbol are alike,marking element will be produced and where they are unlike spacingelements will be produced in the enciphered symbol.

In order to decipher the resultant code combinations transmitted to thedistant receiver, it is necessary to have a key tape at the receivingstation which is identical with that used in enciphering the symbols atthe transmitter. The received permutation code combination for aparticular enciphered character is matched with the same codecombination in the key tape and the original permutation codecombination corresponding to the letter in the text is thereby produced.Thi will become more apparent from the following.

Let it be assumed that the Baudot permutation code combination for aparticular letter in a word in a text to be enciphered is represented bywhere represents a current or marking signal element and represents a nocurrent or spacing signal element. Let it be assumed that thepermutation code combination with which it is combined in the key tapeto form an enciphered permutation code combination is In the encipheringmechanism is arranged so that corresponding like signal element in thetwo combination produce a or marking signal element and unlike elementsproduce or spacing signal element the result and enciphered symbol willbe:

+ Text K y p Enciphered If now the enciphered permutation codecombination is transmitted to a distant station and matched against theidentical code combination in a key tape with which it has beenenciphered in a mechanism which is also arranged to produce a markingsignal element when corresponding signal elements in the receivedenciphered code combination and in the key tape are alike and a spacingsignal element when they are unlike, the permutation code combination ofthe letter of the original text reappears:

+ Enciphered +Keytape Text In order to minimize the possibility of thedeciphering of an enciphered massage by unauthorized persons, it hasbeen determined that a key tape having about one million randomlyoccurring permutation code combinations is required. If one million codecombinations were punched in a single key tape the tape would beexcessively long. The practical equivalent is produced by the use of twokey tapes at each station instead of one. Each of the tapes has slightlyless than one thousand code combinations. The tapes have slightlydifferent numbers of code combinations. Each of the combinations in thefirst key tape at a particular station is combined with a particularcode combination in the second key tape, say the first code combinationtherein, to produce an enciphering code combination which is thencombined with the code combination of the text to produce an encipheredsymbol. Then the second key tape is stepped to the next combination.Each of the code combinations in the first key tape is then combinedwith the second code combination in the second key tape and so on. Thenumber of enciphering code combinations which can thus be produced isequal to the product of the number of code combinations in each tape.The combined lengths and the time and effort of producing the .two. keytapes is thus very considerably reduced as compared with the length ofand the time and effort of producing a single key tape providing acorresponding number of enciphering code combinations. However, the twokey tape arrangement in this respect still leaves much to be desired asthe tapes tear easily and become multilated and worn if used for anyconsiderable length of time.

7 The invention herein corrects this condition by an arrangement whereina system of cams is used for enciphering instead of paper tapes.' Thisis achieved in part by using four sets of five enciph'ering cams each ateach station. The starting positions of each of the cams is adjustablewith respect to the starting position of each of the others. Thisgreatly increases the number of different enciphering sequencesobtainable before repetition is necessary.

As is wellunderstoodin the art, in modern teletypewriter tranmissionsystems, in' addition to transmitting permutation code combinationsrepresenting letters and numbers it is also necessary to transmit othercombinations to perform certain functions. For instance it'is necessaryto transmit a particular code combination to insert a space betweenwords. It is necessary to transmit another particular code combinationto adjust the receiving teletypewriter so that characters are typed onthe succeeding line. Another particular code combination is required toreturn the carriage of the receiving teletypewriter to the normalstarting position. In addition, a particular code combination isrequired to shift the receiving mechanism so that it prints figuresinstead of letters and yet another to readjust the receivingteletypewriter to again print letters.

When the code combinations for the text of a message are combined withthe random enciphering code combinations, any one of the codecombinations which performs the functions enumer ated above may beproduced in random fashion. to Patent 1,416,765, G. S.

Reference is made Vernam, May 23, l922-which discloses an arrangementwherein randomly enciphered teletypewriter code combinationscorresponding to teletypewriter receiver stunt combinations are eachtranslated into two-letter combinations. Further in the arrangement perPatent 1,416,765

the enciphered combinations are arranged in groups of five separated bya space, ten groups to the line. In the arrangement per Patent1,416,765, however, it is necessary to type the enciphered message on ateletypewriter receiver before it can be transmitted. In producing theenciphered message a teletypewriter receiving instrument is actuallypart of the enciphering mechanism. As stunt combinations appear and arerecognized by the sensing circuits in the enciphering circuits,conditions are imposed on various complementary control conductors whichextend into a teletypewriter receiving printer which forms part of theenciphering mechanism, per se. From eight to thirteen conductors areemployed in the various embodiments interconnecting the teletypewriterreceiver and the other parts of the enciphering circuit per Patent1,416,765. In such an arrangement, obviously the teletypewri terreceiver forms part of the enciphering mechanism per se. It iscontrolled over the local conductors and adjusted as necessary inresponse to the adjacent controls to print neat copy. If theteletypewriter enciphering mechanism other than the teletypewriterreceiver in Patent 1,416,765 were in one city and the receiver were in adistan-t city, it would be necessary to interconnect the separatedcomponents of the apparatus 'in Patent 1,416,765 by from eight tothirteen conductors or their equivalent. The arrangement in Patent1,e16,765 is not intended to be and is not operated in such manner, butattention is called to this aspect of the operation of the apparatus ofPatent 1,416,765 in order to point out one of the important aspects ofapplicants invention.

In applicants arrangement it is not necessary to type the encipheredmessage or to punch it'in a tape before it is transmitted. Theenciphered combinations are transmitted directly as they are produced.The randomly appearing stunt combinations are modified as they appearand are transmitteddirectly from the enciphering mechanism to thedistant city without'the intermediary of a teletypewriter receiver.Spaces are introduced between groups of'five combination and line feedand carriage return combinations are introduced after each ten groups offive combinations each without employing a teletypewriter receiver inthe enciphering mechanism per se.

Atthe distant station the enciphered-message, in accordance with thisinvention may be received directly in enciphered form on ateletypewriter receiver which Will print ten groups of five encipheredletters each to a line. If it is desired the message may besimultaneously punched in a tape which is then used to control thedeciphering mechanism which is part of this invention.

If it is preferred the enciphered message may be typed inencipheredform, ten words of five letters each to a line at thetransmitting end. When in this form, the enciphered message may bedelivered to commercial companies for transmission over commerciallines. As an aid in such operation, the apparatus of the inventionherein is arranged so that part of the message, such as the address andsignature maybe in plain text and part may be enciphered. In response tothe appearance of particular sequences of three code combinations,either in the tape bearin the plain text or in the tape bearing theenciphered message the enciphering and. deciphering mechanisms of theinvention herein will-be controlled to shift from plain text to,enciphered combinations and vice versa A feature of this invention is anarrangement in which four sets of cams cooperate in pairs of sets toestablish a resultant enciphering permutation code combination.

Another feature of this invention is an arrangement by means of whichthe starting position of each of the cams of each set is individuallyadjustable with respect to the starting position of each other cam inthe group and the starting position of the cam group is adjustable withrespect to the starting position of other cam groups.

Another feature of the invention is a system of clutches which clutchesare controlled in different manners in response to the random appearanceof functional code combinations in the enciphered text at differenttimes to permit the transmission of other non-functional codecombinations in their stead as well as the introduction of certainfunctional code combinations when required.

Another feature of the invention is an arrangement in which randomlyenciphered permutation code signal combinations including stuntcombinations translated into non-stunt combinations are produced andtransmitted from one station to a distant station without theintermediary of a teletypewriter receiver at the transmitting station.

These and other features will become apparent from the followingdescription when read with reference to the associated drawingsexemplifying one embodiment of the invention, in which:

Fig. 1 is an introductory sketch explaining operations underlying theinvention;

Fig. 2 is a diagram used in explaining the relationship of the majorapparatus units involved in teletyping a message, enciphering themessage, transmitting the enciphered message and receiving an encipheredmessage in enciphered form on a receiving page teletypewriter;

Fig. 3 is a diagram used in explaining the relationship of the majorapparatus units involved in teletyping a message, enciphering themessage, transmitting the enciphered message, receiving the encipheredmessage on a typing reperforator, deciphering the message and receivingthe deciphered message on a receiving page teletypewriter;

Fig. 4 is a diagram showing the manner in which the drawings per Figs. 5to 13 should be arranged, each in relation to the other, to form anoperative system;

Figs. 5 to 13 show the apparatus and circuits of the enciphering anddeciphering system of this invention;

Figs. 14 to 17 are development diagrams used in explaining thearrangement of the four sets of enciphering cams;

Figs. 18 and 19 show details of the enciphering cams and encipheringauxiliar cams respectively;

Fig. 20 shows details of the arrangement for changing the settings ofthe various enciphering cams so as to vary the sequence of theenciphering combinations; and

Figs. 21 to 2'7 are time charts used in explaining the relative times ofoccurrence of various operations.

General description of operation Refer now to Fig. 1 which is anintroductory sketch for use in explaining the basic operationsunderlying the invention.

In Fig. 1 four sets of enciphering cam-operated contacts are shown, camset contacts I, 2, 3 and 4. The cams will be described more fully below.

There are five rotatable cams in each set. Each cam, not shown in Fig. 1controls an individually adjustable element or armature such asarmatures 6 to ID controlled by cam set I. Each armature is operated toengage one or the other of its two contacts such as II or I2, dependingupon the Cutting of its respective cam. Successive permutation codecombinations of the contacts associated with each cam set areestablished in response to the rotation of the cams.

The contacts associated with cam sets I and 2 cooperate as a group tocontrol the operation of relays I5 to I9. Similarly, the contactsassociated with cam sets 3 and 4 cooperate as a group to control theoperation of relays 30 to 34. If a particular cam in cam set No. 2presents a raised surface in a particular position on its periphery toarmature 2I, the armature will be operated so as to engage its contact22. If simultaneously a raised surface on the periphery of the corresponding cam in cam set No. I is presented to armature 6, armature 6will engage contact I2. Under these circumstances a circuit may betraced from ground through contacts 22 and I2 in series and through thewinding of relay I5 to battery, actuating the armature of relay I 5 toengage its contact 23. If the peripher of the cam presented to armature2I in cam set No. 2 is depressed, the armature will engage contact 24.If the periphery of the cam presented simultaneously to armature 6 incam set No. 6 is depressed, armature 6 will engage contact II. Underthese circumstances a circuit may be traced from ground through contacts24 and II in series and the winding of relay I5 to battery, operatingthe armature of relay I5 to engage contact 23 as heretofore. If eitherone of armatures 2| and 6 is actuated to the left and simultaneously theother of these two armatures is actuated to the right there will be nopath available to energize relay I5. Under these circumstances thearmature of relay I5 will engage contact 25. In order to energize arelay such as I 5 therefore it is obvious that each of the armaturessuch as 2I and 6 must be in corresponding positions. The armatures ofrelays I5 to I9 will be operated in conformity with the resultant of thepermutation codes established by the cams of cam sets No, I and No. 2.Similarly, the armatures of relays 30 to 34 will be controlled by camsets 3 and 4.

The code resultant relays 35 to 39 are controlled through thecooperation of relays I5 to I9 and 30 to 34. If the armature of a relaysuch as I5 in one group is actuated to a particular position and thearmature of a corresponding relay such as 30 in another group isactuated to a corresponding position the circuit extending from groundsuch as 4! will be closed through the contacts in series and the windingof relay 35 to battery. If the armature of a relay such as l5 in onegroup is actuated to a particular position and the armature of a relaysuch as 30 in the other group is actuated to a non-correspondingposition the path through the relay contacts will be open and thewinding of the corresponding code resultant relay will be deenergized.

As a result of the above-described operations the resultant of thepermutation codes established by cam sets I, 2, 3 and 4 will be set upby relays 35 to 39. Transmitting contacts to 84 will be setpermutatively in conformity with the permutation code combinations ofthe message text. The armatures of relays 45 to 49 will be controlled bythe settings of contacts 89 :to 84. Ifa contact such as 89v is closed,.a circuit .willbe established from ground through contact-80 andithewinding of .relay 45 tobattery,

operating the armature ofrelay 45 to engagecontact .50. If a contactsuch as 80 is open the armature of a relay such as 45 will be actuatedto engage a contact such as 51. The code combinations established on thearmatures of relays 45 to 49 will be combined with the encipheringresultant code combinations established by relays 35 to 39. If thearmatures ofrelays in corresponding positions on the message text relays45 to 49 and on the enciphering code resultant relays 35 to 39 are bothin corresponding positions, circuits will be established from groundthrough contacts such as 85 and 50 in series and the winding of a relaysuch as relay 55, closing contact 60. If the armatures of relays such as35 and are not actuated to corresponding positions, there will be noclosed path available foroperating a corresponding relay such as relay55. The permutation code combinations established by combining thepermutation code combination of the message text with the permutationcode combination resulting from the operation of cam sets I to 4 will beestablished on the armatures of relays 55 to 59.

.If all that were required were the transmission of encipheredpermutation code combinations resulting from the modification of themessage text code combinations'by the resultant enciphering codecombinations, the code combinations appearing on the code resultantrelays 35 to 39 could be combined directly with the code combinationsappearing on the message text transmitting contacts 89 to 84. The threegroups of relays, namely, the ciphered text transmitting relays 45 to19, the storing relays 55 to 59 and the distributor relays 95 to 59 areintroduced to permit the sensing of the enciphered text code combinationto detect, among the random code combinations appearing, thecodecombinations which would if transmitted cause a receiving teletypewriterto respond by returning its carriage to the starting position, operatingthe line feed mechanism operating the spacing mechanism, shifting to theupper or lower case or introducing a space at undesired times. In short,these relaysprevent the random transmission of functional or stuntcombinations as they are known in the art and introduce functionalcombinations at proper times to print the enciphered text in a neatpattern, namely, in five-character groups, ten groups to a line.

In order to perform these functions considerable apparatus in additionto that disclosed in Fig. 1- and shown on the detailed circuit andapparatus drawings herein is required. For instance, in order todetermineif a stunt code combination has been established at random onrelays 55 to 59, circuitsare established in series through contacts,which are shown only in the more detailed drawings, when the stunt codecombination appears. Under such circumstances the stunt code combinationis not transmitted. The single stunt combination is replaced by atwo-letter combination. The first letter of the two-letter combinationis always an E. The second letter may be any one of five lettersdepending upon the particular function. The combination corresponding tothe function is changed by modifying the fifth element of thecombination.

In order to do this, that is, permit the translation of a random stuntcode combination into two rcodetcombinations, the invention herein isarrangedso that each .of the randomly enciphered code combinationsappearing on relays 55 to 59 is sensed to detect a stunt combinationwhile the preceding code combination is being transmitted.

The transfer of the code combinations appearing on relays 55 to 59 tothe distributor relays included in the detailed drawings.

65 to 69 in proper order and the transmission of the code combinationsare under control of distributor 19. This distributor has two pairs ofrings. These rings are indicated in the developed condition. One pair ofrings, solid ring H and segmented ring '52, which are connected to thesingle transmission channel formed by the two line conductors, controlsthe transmission of the enciphered code combinations. The second pair ofrings, grounded solid ring 13 and segmented ring 14, controls the timesof transfer of the enciphered code combinations from the group of relayscomprising relays to 59 to the group of relays comprising relays to 69.Rings H and '12 are interconnected by one pair of brushes i6 and H andrings I3 and M are interconnected by a second pair of brushes i8 and 19.Both pairs of brushes are carried by one rotatable arm, not shown inintroductory Fig. 1 but indicated as arm IUI in Fig. 6.

If a code combination appearing on the contacts of relays 55 to 59, whensensed by the series circuit through auxiliary contacts on these relaysshown in the more detailed drawings, is not a stunt combinationappearing at random, after the preceding code combination has beentransmitted by means of relays 65 to 69 and distributor rings 12 and H,the code combination will be transferred at the proper time undercontrol of rings 13 and 14 to the transmitting mechanism. It will thenbe transmitted. If, however, it is a random stunt combination, thecombination. corresponding to the letter E Will be established on relays65 to 69 as soon as the preceding character has been transmitted. Duringthis interval the code combination corresponding to therandom stunt Willbe modified by changing the fifth'element only. The changing f the fifthelement of any of the five stunt combinations results in the formationof a code combination corresponding to a particular one of five-lettercombinations. Then the resulting letter combination will be transferredto the transmitting a paratus for transmission as the second letter ofthe two-letter combination substituted for the random stunt combination.

The above will'serve as an introduction to the detailed description tofollow.

It is pointed out that in order to performother functions such as tointroduce a combination fora space at the proper interval, to separatethe code combinations into groups of five symbols (or code words as theywill be called herein) and in order to introduce proper codecombinations at the end of a line, etc., a counting mechanism, a systemof clutches and controls therefor are Further, the substitution of twocombinations for one introduces complications. For instance, acomplication arises when a, random stunt combination occurs in positionto be transmitted as the fifth elementof a codeword and the letter E andthe second letter of the two-letter combination must be separated by aspace. Another occurs when a random stunt combination appears inposition for transmission as the last combination in the last code wordof a line. Caring for these and other conditions requires that thesystem Of Fig. 1 be elaborated into the detailed system of the inventionshown on the other drawings herein which will now be described.

Refer now to Fig. 4. Fig. 4 shows the manner in which Figs. to 13,inclusive, should be arranged each in relation to the other to form anoperative system.

The keys in Fig. 5 may be operated in different manners to obtaindiiferent operating arrangements as shown in Figs. 2 and 3.

In the arrangement shown in Fig. 2 a sending and receiving pageteletypewriter equipped with a perforator is indicated by the left-handrectangle. It is connected to a cipher unit which enciphers andtransmits the message.

The cipher unit transmits the message to a receiving-only pageteletypewriter which prints the enciphered message in five-letter codewords, ten Words to a line. The receiving-only page teletypewriter isrepresented by the right-hand rectangle. It may be located at the samestation as the enciphering apparatus shown in the two left-handrectangles, or if desired, if may be located at the office of the localcommercial telegraph company or at an oflice in a distant city. Theenciphered message in this form may, if desired, be transmitted over thefacilities of a commercial telegraph company. Thereafter, the receivedmessage may be deciphered and printed as it appeared in the originaltext by running the message through the ciphering unit and modifying itby means of the code combinations resulting from cam settingscorresponding to those used in originally enciphering the text.

Fig. 3 shows an arrangement wherein, as represented by the successiverectangles from left to right, a sending and receiving pageteletypewriter with perforator, perforates and records a plain textmessage. The plain text message is impressed on the cipher unit whichenciphers and transmits the message directly to a distant station. Theenciphered message is received in the distant station by a typingreperforator which reperforates and prints the ciphered message. Theciphered message is impressed on the cipher unit which deciphers themessage. Then the deciphered message is received on a receiving-onlypage teletypewriter which prints the deciphered message.

The reference numeral 521 in Fig. 5 represents a teletypewriter setwhich comprises a receiving printer, a keyboard operated type perforatorand a keyboard operated transmitter. A set which combines these units isdisclosed in Patent 1,965, 572 granted July 10, 1934, to C. W. Burcky etal. The receiving printer unit which is contemplated in the Burcky eta1. patent is disclosed in full detail in Patent 1,904,164, grantedApril 18, 1933, to S. Morton et al.

The reference numeral 525 in Fig. 5 represents a receiving-onlyteletypewriter. Such a receiving teletypewriter is disclosed also in theabove-mentioned Patent 1,965,572.

The reference numeral 526 in Fig. 5 represents a typing reperforator.Such a mechanism is disclosed in Patent 2,273,909, granted February 24,1942, to C. W. Swan.

The reference numeral 625 in Fig. 7 represents a tape transmitter. Sucha transmitter is disclosed in Patent 2,055,567 granted September 29,1936 to E. F. Watson.

The disclosures of the aforementioned patents The cipher unit isindicated by the middle rectangle.

are incorporated herein by reference as part of the presentspecification.

With the keys in Fig. 5 in the positions shown, a circuit may be tracedfrom battery 50! through the receiving selector magnet 502, contact 503of key 504, teletypewriter transmitting contacts 505 and contact 506 ofkey 584 to ground 501, energizing the sending and receivingteletypewriter. The sending and receiving teletypewriter is equippedwith a well-known perforator which perforates the code combinations ofthe characters and stunt functions of the message typed on theteletypewriter in a well-known manner. The perforated tape is stored ona storage reel 598. The perforated tape containing the messageto beenciphered is then transferred to a perforated tape supply reel 101 inFig. 7 and is run over roller 102 through tape lever roller 103 androller 104 over the sensing pins 105 to 109 under the influence of thetape feed mechanism H0 in a manner to be described more in detailhereinunder. The code combinations appearing in the tape are modified bythe mechanism of the ciphering unit in a manner to be described and areimpressed on the transmitting distributor 60]. The enciphered signalsare impressed on a circuit which may be traced from ring 602 of thedistributor through conductor 603 into Fig. 5 where the circuit extendsthrough contacts 509 and 5 ID of key 504, contact 5| I of key 512through selecting magnet 5l3 of the receiving-only teletypewriter 525,through contact 5M of key 5| 2, contact 5! 5 of key 5IB through theselecting magnet 5il of the typing reperforator 526, contact 518 of key5|6, contact 5I9 of key 520 and resistance 52! to battery 522. Theopposite side of the transmitting circuit extends through brushes 604and 605 in series through the outer ring of distributor 6M, conductor606 which extends into Fig. 5 and through contact 523 of key 520 toground 524. Under these circumstances, the enciphered message will beprinted by the receiving-only teletypewriter 525 and will bereperforated by the typing reperforator 526. This setup correspondsgenerally to the arrangement shown in Fig. 2 except that a typingreperforator is connected into the system also so that the encipheredmessage will be both printed on the receiving-only teletypewriter andreperforated by the typing reperforator.

While the system is thus arranged, a distant teletypewriter switchingsystem indicated by rectangle 528 is connected by means of conductors529 and 530 through loading 53! in such manner that a calling signal 532may be operated to signal an incoming message. Conductor 529 is extendedthrough resistance 533 and contact 534 of key 526 through calling signal532 to ground. Conductor 530 i connected through contact 535 of key 520to ground.

The keys may be operated in a manner to provide the arrangementindicated in Fig. 3. For this condition, as indicated in Fig. 3 afterthe message has been typed and reperforated and thereafter enciphered,it is transmitted to a distant station. In order to transmit from theciphering unit to a distant station, keys 5l2, 5| 6 and 520 in Fig. 5are actuated. The transmitting distributor is then connected throughconductor 603, contacts 509 and 5H) of key 504, contacts 536 and 53! ofkey 5l2, contacts 538 and 539 of key 5! 6, contact 540 of key 520 andresistance 533 to conductor 529 which extends to the distant station.Conductor 606 is extended through contact 541 to conductor 530 whichextends also

